Since the identification of human immunodeficiency virus type 1 (HIV-l) as the etiologic agent of the acquired immunodeficiency syndrome (AIDS), much progress has been made in elucidating the molecular biology and structure of this virus. However, the mechanisms responsible for protection against the virus are poorly understood. The rational design of AIDS vaccines, an effective form of immunologic intervention in other viral diseases, requires understanding these defense mechanisms, particularly T cell- mediated immunity, which plays an important role in protection against enveloped viruses. Studies are hereby proposed to address these questions in two directions: First, detailed mapping of, and analysis of genetically determined responsiveness to, antigenic determinants in the gp41 and gp120 envelope glycoproteins of HIV- l recognized by murine and human T helper (Th) cells and cytotoxic T lymphocytes (CTL) will be performed. Th epitopes will be mapped by a combination of in vivo immunization and in vitro T cell proliferation assays, while CTL sites will be defined by generating primary CTL responses in culture against short synthetic peptides. The use of overlapping peptides covering the entire amino acid sequence of the relevant proteins as immunogens, and a sufficiently large number of major histocompability complex (MHC) haplotypes ensure that a majority of potential T cell epitopes, including minor ones, will be revealed. Second, this proposal will explore several strategies designed to potentiate the immunogenicity of synthetic peptide AIDS vaccines, to overcome the MHC-determined genetic unresponsiveness to them at the T cell level, and to convert peptides representing a com- bination of native T and B cell epitopes into complete immunogens in the absence of conventional carrier proteins. These approaches include covalent coupling of gp41- or gp120-derived peptides to: a) Azobenzenearsonate or related compounds, shown to function as efficient, relatively MHC-unrestricted, Th epitopes, or; b) antibodies that will target such peptides to antigen-presenting B cells and/or macrophages; c) inclusion of the T cell activating cytokines interleukin 1 or 2 in synthetic peptide vaccines; and d) evaluation of lipid A-associated hydrophobic outer membrane proteins from E. coli as immunological adjuvants that can bypass the need for oil emulsions and other unacceptable adjuvants. The proposed studies could constitute a step towards the formulation of effective and highly immunogenic synthetic vaccines against AIDS and other infectious diseases.